Despite significant advancement in our understanding of the phonation process in general, it still remains unclear how changes in individual geometrical and material properties of the vocal system affect vocal fold vibration and voice production. Our current understanding of phonation is largely based on results obtained from lumped-mass or other simplified phonatory models. These models have successfully identified key elements and features of phonation. However, parameters that are central to these models often cannot be directly measured or easily related to the anatomical structure or material properties of the vocal folds. Due to this lack of correspondence between model parameters and realistic, directly measurable properties of the vocal folds, direct translation of model-derived findings to clinical applications has been problematic. As a result, speech-language pathologists and surgeons often must rely heavily on experience and their subjective impressions of vibratory pattern to diagnose and treat voice disorders. The long-term goal of the proposed research is to establish a direct link between the underlying geometrical and material properties of the vocal folds and the resulting vocal fold vibration, acoustics, and voice quality. The two main questions to be addressed are: 1) How do changes in the geometrical and material properties of the vocal folds, due to either pathologies or surgical procedures, affect vocal fold vibration and voice quality? and 2) What features of the vocal fold vibration are physically related to the geometrical and material properties of the vocal folds and therefore useful for diagnosis of voice disorders and their ultimate management? Over a five-year period, we propose to answer these two main questions by addressing the following three Specific Aims: 1) Determine the influence of vocal fold geometrical and material properties on the resulting vocal fold vibration, acoustics, and voice quality; 2) Quantify the influence of left-right asymmetries in vocal fold geometrical and material properties on the resulting vocal fold vibration, acoustics, and voice quality; 3) Determine the influence of localized changes in vocal fold properties on the resulting vocal fold vibration, acoustics, and voice quality.